Thin Film Transistor Liquid Crystal Display (TFT-LCD) is a flat-panel display device, and is more frequently applied to high-performance display field due to its advantages such as small size, low power consumption, no radiation and relatively low fabrication cost.
As shown in FIG. 1, a TFT 10 comprises a gate electrode 100, a gate insulating layer 101 and a semiconductor active layer 102 which are sequentially provided on the gate electrode 100, and a source electrode 103 and a drain electrode 104 respectively provided on both sides of the semiconductor active layer 102. In the case that a voltage applied to the gate electrode 100 is greater than or equal to a threshold voltage of the TFT 10, the semiconductor active layer 102 forms a conductive path, so that the source electrode 103 and the drain electrode 104 are connected with each other and the TFT 10 is turned on.
In order to prevent electrical properties of the TFT 10 from being affected, it is necessary to protect a surface of the semiconductor active layer 102; because a SiO2 (silicon dioxide) thin film has excellent electrical insulating properties and fabrication feasibility, a SiO2 passivation layer 105 made of SiO2 is generally formed on the semiconductor active layer 102.
However, in a process of depositing the SiO2 thin film, oxidation is accelerated due to the temperature, so the formed SiO2 thin film has relatively loose structure. Therefore, there are a lot of holes on the surface of the SiO2 thin film, resulting in decrease of adhesion of the surface of the SiO2 thin film. In this way, in a process of forming a pixel electrode layer 106 on the surface of the passivation layer 105 made of SiO2 by a patterning process, the pixel electrode layer 106 may peel off during removing a photoresist covering a pattern of the pixel electrode layer, thus seriously affecting product quality.